NIT visible in analyse mode but not in scan selected

[palinf]

Hi,

 

I use Transedit 4.0.4.0 and I would like to understand the things.

I am pretty new to DVBC concept but what I understood so far is:

Some frequency carry NIT which can be use to set up/discover transponder information ( frequency (f) , symbol rate(sr) and modulation(mod) )

 

I understood Transedit can add transponder directly in the transponder list when NIT is found.

 

Q1: So far, am I correct ?

 

I set up the f, sr and mod according to my set-top box and did:

a. A scan (by pressing scan). The NIT indicator stay red.

b. An analysis (by pressing analyse). I clearly see a NIT and some transponder information. I did an analysis of those transponder and they carry channels.

 

Q2: Is this correct to suspect an underlying problem ?

 

Q3: Is there an easy way to extract transponder information from NIT and add them to the transponder list for future scan/analysis.

 

Thanks,

 

[Griga]

Q1: Yes, when using the update function or Settings -> Scanner -> Scan NIT and update transponders while scanning.

 

Q2: Yes. A red NIT field indcates that reading the NIT failed for some reason. Maybe the NIT timeout is too short (see Settings -> Scanner).

 

For checking other possible reasons I would need a sample. Launch the Analyzer, wait until all streams have appeared, right-click the PID list, click "Select Main SI PIDs" in the context menu, record them for a minute or so and upload the resulting TS file to some web space. To keep the file small you may want to unselect the EIT stream (by holding down the Ctrl key while clicking it) before you start recording because it is not necessary in this case.

 

Q3: Yes, it should happen automatically if scanning the NIT works as intended (see Q1).

[palinf]

NIT timeout has been set to 60sec and scanning still fail.

 

I dropped the analyse file here:

http://www.sendspace.com/file/30nsjb

or

http://dl.free.fr/nnQYcn6Wc

 

I kept the EIT as it does not represent a large volume on this dump.

[Griga]

Your sample doesn't contain a NIT for the actual network. Looks like the cable provider only broadcasts a NIT for other networks. Maybe it contains information about the actual network (the one you are receiveing), but it is flagged as a NIT for other networks.

 

The scanner only reads data that applies to the actual network, of course. Usually it looks like the screenshot below. Read more about it here.

[palinf]

Yes, inside the NIT flagged as other network is the network I receive with the classical set top box.

 

Then, is there a way to easily extract the info for NIT other network for further parsing ? Either by the software or by trick (like applying an xslt on the xsl or a sed to the copy/pasted information from DVBViewer ?)

 

Regards,

Edited December 6, 2013 by palinf

[Griga]

is there a way to easily extract the info for NIT other network for further parsing ?

 

You could export the NIT node as xml (right-click it -> Save as XML) and write a script / program that reads the information and converts it to an INI transponder list file. However, that's some work and requires knowledge about the NIT structure.

 

Another possibility would be a flag in the transponder list file telling the TransEdit scanner that it shall read the NIT for other networks. I will think about it...

[palinf]

 

 

Another possibility would be a flag in the transponder list file telling the TransEdit scanner that it shall read the NIT for other networks

Nice evolution indeed (: I doubt I will benefit from it before weeks so I will have a look on a quick parser.

 

Another thing would maybe change the information which define the nit table from other network to actual network in the .ts file... Would this be quicker ? Is this only a pair of hex code to switch from a value to another ?

[Griga]

Another thing would maybe change the information which define the nit table from other network to actual network in the .ts file... Would this be quicker ?

 

Dunno how good you are in manipulating binary files... you can see it in the TransEdit Hex Viewer (right-click the stream in question in the Analyzer -> Hex View). The table ID for "other" NIT sections is 0x41 (first byte after the yellow one). The table ID for "actual" NIT sections is 0x40. It has to be changed for all NIT sections, which means, you have to find out where they start in the file, which means, you need profound knowledge about how a TS and SI tables are structured.

 

And another drawback: It would require scanning the modified file. TransEdit is able to do it, but the scanner can't do anything with the results because there is no transponder list associated with a TS file. So... forget it.

[palinf]

Ok.

Then could you provide me with an advice on this solution:

 

Extract every value of group of tag (Frequency, Modulation, Symbolrate)

from xml copy/pasted and create

a classic transponder list

using an xslt.

Then use classic scanning on this transponder list.

Let me know if you see any drawback with this solution.

[Griga]

Well, I don't know xslt. In theory it should work, because usually the NIT provides the input that is required for a transponder list as output.

 

However, in your case... questionable. I had another look at your file and saw some things that are not DVB compliant. Seems the cable provider is using a proprietary variation of the DVB standard. Particularly some IDs don't match:

 

PAT: TransportStreamID = 346

SDT - Actual TS: TransportStreamID = 306, OriginalNetworkID = 9

EIT - Actual TS: TransportStreamID = 346, OriginalNetworkID = 19

 

These values should be identical, but they aren't. As a result the scanner doesn't work correctly (proved by letting it scan your file) , and DVBViewer will not be able to assign EPG data to channels, which simply means, you will get no EPG for some or all channels. The whole thing smells like trouble that can (probably) only be avoided by entering / correcting channel data manually. Sorry, no better news...